ok I exchanged my NEC PCI 4+1 for a ALi PCI 4+1 with the following ID :
## Vendor Device Vendor name Description
13 0x10B9 0x5237 ALi Corporation USB 1.1 Controller
14 0x10B9 0x5237 ALi Corporation USB 1.1 Controller
15 0x10B9 0x5237 ALi Corporation USB 1.1 Controller
16 0x10B9 0x5239 ALi Corporation USB 2.0 Controller
and now all is fine, my USB stick is running at 2.0 speed as you can see below :
scsispeed DRIVE usbdisk.device:0 FAST BUF1=8192 BUF2=16384 BUF3=32768 BUF4=65536
MKSoft ScsiSpeed 4.2 Copyright © 1989-92 MKSoft Development
AmigaOS4 port by Stéphane Guillard
------------------------------------------------------------
CPU: 68020 AmigaOS Version: 53.22
Device: usbdisk.device:0
Testing with a 8192 byte, MEMF_FAST, LONG-aligned buffer.
Read from SCSI: 2571468 bytes/sec
Testing with a 16384 byte, MEMF_FAST, LONG-aligned buffer.
Read from SCSI: 4341760 bytes/sec
Testing with a 32768 byte, MEMF_FAST, LONG-aligned buffer.
Read from SCSI: 6850150 bytes/sec
Testing with a 65536 byte, MEMF_FAST, LONG-aligned buffer.
Read from SCSI: 9637068 bytes/sec